This article deals with Finnish-language surnames (family names) in Sweden. These may be borne by Finnish immigrants or their descendants, or by members or descendants of the Tornedalian minority group in the north of Sweden. In this study, the 20 commonest Finnish-language surnames in Sweden as a whole, the 20 commonest Finnish-language surnames in Norrbotten county in the northernmost of Sweden, and the 20 commonest surnames in Finland are compared. This shows that the top-20 surnames of Norrbotten county and of Finland differ to quite a large extent. While the commonest surnames in Finland often ends in the suffix –nen, a suffix that was widespread in Finland during the times of nation-building in the last decades of the 1900th century, the commonest Finnish-language surnames in Norrbotten county are usually simplex names. A study of the 1880, 1890, 1900 and 1910 Swedish censuses shows that the Finnish-language surnames common in Norrbotten county is also those of long history in Sweden. It is concluded that the Finnish-language surnames in Sweden consists of two layers, the Tornedalian minority surnames and the Finnish immigrant surnames, even though some surnames belong to both those groups.